Plan should better diff the embedded template attribute

[regner]

Currently when you run nomad-pack plan the EmbeddedTmpl value is flattened into a single line string. If there is a change someone in this string, then that single line contains the before and after. These templates can get long and so it can be very hard to identify what the change is.

Ideally the plan command would print out the value of EmbeddedTmpl with the new lines and show a diff of what lines have changed.

I currently accomplish this with a bash script that I pipe the output of plan through:

#!/bin/bash

# Extract the EmbeddedTmpl line
combinedTemplates=$(sed -nE 's/.*EmbeddedTmpl: +(.*)/\1/p')

if [ -n "$combinedTemplates" ]; then
    before=$(echo "$combinedTemplates" | sed -nE 's/(.*) => (.*)/\1/p')
    after=$(echo "$combinedTemplates" | sed -nE 's/(.*) => (.*)/\2/p')

    # Run diff and display output
    diff_output=$(colordiff --unified <(echo "${before@E}") <(echo "${after@E}"))

    if [ -z "$diff_output" ]; then
        echo "No differences found."
    else
        echo "Differences:"
        echo "$diff_output"
    fi
else
    echo "EmbeddedTmpl line not found in input."
fi

My workflow then is:

• Run nomad-pack plan ... as normal
• If there is a change to the EmbeddedTmpl I run nomad-pack plan ... | ./templatediff.sh

Here is a sample output without my script:

nomad-pack plan -f packs/robomerge/variables/production.hcl packs/robomerge/
+/- Job: "robomerge"
+/- Task Group: "robomerge" (1 create/destroy update)
  +/- Task: "robomerge" (forces create/destroy update)
    +/- Template {
          ChangeMode:    "restart"
          ChangeSignal:  ""
          DestPath:      "secrets/file.env"
      +/- EmbeddedTmpl:  "{{ with nomadVar \"nomad/jobs/robomerge\" }}\nROBO_HOST_INFO=\"robomerge\"\nROBO_EXTERNAL_URL=\"SOME_INTERNAL_URL\"\nROBO_RUNBOTS=\"yes\"\nROBO_PREVIEW_ONLY=\"false\"\n\nBOTNAME=\"project_one,project_two\"\n\nROBO_WATCHDOG_PORT=\"8080\"\n\n# InfluxDB
settings\nROBO_INFLUX_AUTHORIZATION={{ .INFLUX_AUTHORIZATION }}\nROBO_INFLUX_URL={{ .INFLUX_URL }}\n\n# Internal path settings, where Robomerge stores things\nROBO_VAULT_PATH=\"/robomerge/vault\"\nROBO_BRANCHSPECS_DIRECTORY=\"/robomerge/branchspecs\"\nROBO_PERSISTENCE_DIR=\"/robomerge/persistence\"\n\n#
Perforce path settings\nROBO_BRANCHSPECS_ROOT_PATH=\"//PERFORCE/PATH\"\nROBO_PERSISTENCE_BACKUP_PATH=\"//OTHER/PERFORCE/PATH\"\n\n# Perforce workspace
settings\nROBO_BRANCHSPECS_WORKSPACE=\"robomerge-branchspec\"\nROBO_PERSISTENCE_BACKUP_WORKSPACE=\"robomerge-persistencen\"\n\nROBO_NO_MAIL=\"true\"\n\n# Sentry
configuration\nEPIC_ENV=\"prod\"\nNODE_ENV=\"production\"\nEPIC_DEPLOYMENT=\"production\"\nSENTRY_DSN=\"SENTRY_DSN_URL\"\n\n# Perforce configuration\nP4PORT={{ .P4_PORT }}\nP4USER={{ .P4_USER }}\nP4PASSWD={{ .P4_PASSWORD }}\n{{ end }}\n" =>
"{{ with nomadVar \"nomad/jobs/robomerge\" }}\nROBO_HOST_INFO=\"robomerge\"\nROBO_EXTERNAL_URL=\"SOME_INTERNAL_URL\"\nROBO_RUNBOTS=\"yes\"\nROBO_PREVIEW_ONLY=\"false\"\n\nBOTNAME=\"project_one,project_two,project_three\"\n\nROBO_WATCHDOG_PORT=\"8080\"\n\n# InfluxDB
settings\nROBO_INFLUX_AUTHORIZATION={{ .INFLUX_AUTHORIZATION }}\nROBO_INFLUX_URL={{ .INFLUX_URL }}\n\n# Internal path settings, where Robomerge stores things\nROBO_VAULT_PATH=\"/robomerge/vault\"\nROBO_BRANCHSPECS_DIRECTORY=\"/robomerge/branchspecs\"\nROBO_PERSISTENCE_DIR=\"/robomerge/persistence\"\n\n#
Perforce path settings\nROBO_BRANCHSPECS_ROOT_PATH=\"//PERFORCE/PATH\"\nROBO_PERSISTENCE_BACKUP_PATH=\"//OTHER/PERFORCE/PATH\"\n\n# Perforce workspace
settings\nROBO_BRANCHSPECS_WORKSPACE=\"robomerge-branchspec\"\nROBO_PERSISTENCE_BACKUP_WORKSPACE=\"robomerge-persistencen\"\n\nROBO_NO_MAIL=\"true\"\n\n# Sentry
configuration\nEPIC_ENV=\"prod\"\nNODE_ENV=\"production\"\nEPIC_DEPLOYMENT=\"production\"\nSENTRY_DSN=\"SENTRY_DSN_URL\"\n\n# Perforce configuration\nP4PORT={{ .P4_PORT }}\nP4USER={{ .P4_USER }}\nP4PASSWD={{ .P4_PASSWORD }}\n{{ end }}\n"
          Envvars:       "true"
          ErrMissingKey: "false"
          LeftDelim:     "{{"
          Perms:         "0644"
          RightDelim:    "}}"
          SourcePath:    ""
          Splay:         "5000000000"
          VaultGrace:    "0"
        }

And the output with my script:

nomad-pack plan -f packs/robomerge/variables/production.hcl packs/robomerge/ | ./templatediff.sh 
Differences:
--- /dev/fd/63  2025-09-05 10:36:47.716217407 +0000
+++ /dev/fd/62  2025-09-05 10:36:47.716217407 +0000
@@ -54,7 +54,7 @@
 ROBO_RUNBOTS="yes"
 ROBO_PREVIEW_ONLY="false"
 
-BOTNAME="project_one,project_two"
+BOTNAME="project_one,project_two,project_three"
 
 ROBO_WATCHDOG_PORT="8080"

My script cuts out all the other changes, so still requires I run a normal plan before I pass it through my script.

[tgross]

@regner I'm going to move this issue over to the Pack repo, rather than the community registry repo, to make sure it gets triaged appropriately.

[regner]

Crap, I am so sorry. I had both repos open and must have made the issue on the wrong one. Thank you for moving it.

[tgross]

I took a quick look at this and it looks like we're using similar logic to what's being done in Nomad proper with the nomad job plan command. It's an independent implementation but both have the same ugly formatting behavior (or lack thereof). The API returns \n within the diff but then the Nomad CLI, the Nomad UI, and Nomad Pack all escape that newline.

So this is similar to hashicorp/nomad#23603, hashicorp/nomad#23851 (unfortunately closed), hashicorp/nomad#18103, and hashicorp/nomad#4421 but actually has to get fixed independently in Pack. I'll mark this for roamdmapping.